In an electronic data storage and retrieval system, a transducing head typically includes a writer for storing magnetically-encoded information on a magnetic disc and a reader for retrieving that magnetically-encoded information from the magnetic disc. The reader typically consists of two shields and a magnetoresistive (MR) sensor positioned between the shields. Magnetic flux from the surface of the disc causes rotation of the magnetization vector of a sensing layer of the MR sensor, which in turn causes a change in electrical resistivity of the MR sensor. This change in resistivity of the MR sensor can be detected by passing a current through the MR sensor and measuring a voltage across the MR sensor. External circuitry then converts the voltage information into an appropriate format and manipulates that information as necessary.
The writer portion typically consists of a top and a bottom pole, which are separated from each other at an air bearing surface of the writer by a gap layer, and which are connected to each other at a region distal from the air bearing surface by a back gap closer or back via. Positioned between the top and bottom poles are one or more layers of conductive coils encapsulated by insulating layers. The writer portion and the reader portion are often arranged in a merged configuration in which a shared pole serves as both the top shield in the reader portion and the bottom pole in the writer portion.
To write data to the magnetic media, an electrical current is caused to flow through the conductive coils to thereby induce a magnetic field across the write gap between the top and bottom poles. By reversing the polarity of the current through the coils, the polarity of the data written to the magnetic media is also reversed. Because the top pole is generally the trailing pole of the top and bottom poles, the top pole is used to physically write the data to the magnetic media. Accordingly, it is the top pole that defines the track width of the written data. More specifically, the track width is defined by the width of the top pole near the write gap at the air bearing surface.
In magnetic recording, it is desirable to improve the areal density at which information can be recorded and reliably read. This desire has led to a trend toward shorter bit length along a magnetic recording track and a shrinking track width. Narrow track widths are achieved by use of narrow pole tips at an air bearing surface (ABS) of the head.
Elements of conventional writers do not properly contain the magnetic flux within the elements themselves and part of the flux leaks into adjacent elements. The result of this leakage is unintentional erasure of side tracks due to the parasitic field established near the susceptible soft under-layer structure within the media. Additionally, the need to increase magnetic recording density results in reducing the size of the read element and shields, causing instability of the domain wall structure. This instability leads to degradation of head performance and increased error rate. Thus, in conventional head designs, there exists increased parasitic affects from the size and shape of the write portion components and reduced magnetic stability of the read portion leading to low head performance and side track erasure.
Therefore, elements of the recording head need to be sized and positioned such that the parasitic field may be reduced or eliminated by improving the spin structure to be less susceptible to dynamic distortion and the read portion needs to provide a more stable magnetic shield having high permeability.